Spraying council drains

We maintain a network of 330km of council open drains that run alongside roads and across private farmland. Maintenance of the drains include spraying twice a year to keep them free from weeds. Keeping the weeds down helps keep stormwater draining and avoid flooding.

Our contractor sprays with a broad-spectrum herbicide - Glyphosate (Roundup™) in spring and autumn - September - October and March - April. We use Roundup™ as it is one of the safer chemicals to use in waterways.

We put signs up where we spray advising people not to pick watercress.

No picking watercress

It is not safe to pick any watercress from roadside drains or private property unless it's on your own land and you know that it's free of spray.

Also don't buy watercress unless you know where it has been picked from.

Be aware that farmers also spray their drains on the Poverty Bay Flats for weeds and they don't put signs up warning they have sprayed.